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expression, plan: aggressive constant fold for null parameter expression to simplify outer join #7696

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merged 24 commits into from
Sep 23, 2018
Merged

expression, plan: aggressive constant fold for null parameter expression to simplify outer join #7696

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4653f81
expression: try to fold constant for expression with null parameter
eurekaka Sep 8, 2018
b23e33d
substitute non-Constant arg to One
eurekaka Sep 8, 2018
26cc553
add PruneColumns for LogicalTableDual
eurekaka Sep 8, 2018
6260ca0
disable TestPreparedNullParam for plan cache enabled setting
eurekaka Sep 8, 2018
ce4033e
push down not first before foldConstant
eurekaka Sep 8, 2018
615d985
revert PruneColumns of LogicalTableDual, this would be in another PR
eurekaka Sep 8, 2018
6effd4f
move PushDownNot to isNullRejected to avoid stack overflow
eurekaka Sep 8, 2018
fbef1a3
update tpch explain test because left outer semi join is converted to…
eurekaka Sep 8, 2018
0304e81
add unit test and explain test
eurekaka Sep 8, 2018
21f75ca
resolve conflicts
eurekaka Sep 9, 2018
be77917
resolve conflicts
eurekaka Sep 9, 2018
33190d3
update TestOuterWherePredicatePushDown since it would be simplified t…
eurekaka Sep 9, 2018
b6825da
fix compilation error
eurekaka Sep 9, 2018
2feffbe
index out of range
eurekaka Sep 9, 2018
9a781b5
fix index out of range
eurekaka Sep 9, 2018
fb05e5a
Merge branch 'master' into const_prop_simplify_outer
eurekaka Sep 20, 2018
210f8d5
use NewFunctionInternal instead of Clone
eurekaka Sep 9, 2018
14826cd
Merge branch 'master' into const_prop_simplify_outer
eurekaka Sep 20, 2018
84b357c
Merge branch 'master' into const_prop_simplify_outer
eurekaka Sep 20, 2018
33c620a
address comments
eurekaka Sep 9, 2018
a6302bd
Merge branch 'master' into const_prop_simplify_outer
eurekaka Sep 21, 2018
d4a3200
do not fold null for nulleq function
eurekaka Sep 9, 2018
c900e9c
Merge branch 'master' into const_prop_simplify_outer
zz-jason Sep 21, 2018
8bbcdfe
Merge branch 'master' into const_prop_simplify_outer
zz-jason Sep 23, 2018
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5 changes: 5 additions & 0 deletions cmd/explaintest/r/explain_easy.result
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Original file line number Diff line number Diff line change
Expand Up @@ -352,6 +352,11 @@ create table t(a bigint primary key);
explain select * from t where a = 1 and a = 2;
id count task operator info
TableDual_5 0.00 root rows:0
explain select null or a > 1 from t;
id count task operator info
Projection_3 10000.00 root or(NULL, gt(test.t.a, 1))
└─TableReader_5 10000.00 root data:TableScan_4
└─TableScan_4 10000.00 cop table:t, range:[-inf,+inf], keep order:false, stats:pseudo
drop table if exists ta, tb;
create table ta (a varchar(20));
create table tb (a varchar(20));
Expand Down
92 changes: 45 additions & 47 deletions cmd/explaintest/r/tpch.result
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Original file line number Diff line number Diff line change
Expand Up @@ -184,38 +184,37 @@ limit 100;
id count task operator info
Projection_34 100.00 root tpch.supplier.s_acctbal, tpch.supplier.s_name, tpch.nation.n_name, tpch.part.p_partkey, tpch.part.p_mfgr, tpch.supplier.s_address, tpch.supplier.s_phone, tpch.supplier.s_comment
└─TopN_37 100.00 root tpch.supplier.s_acctbal:desc, tpch.nation.n_name:asc, tpch.supplier.s_name:asc, tpch.part.p_partkey:asc, offset:0, count:100
└─Selection_38 100087.54 root eq(tpch.partsupp.ps_supplycost, min(ps_supplycost))
└─HashLeftJoin_39 125109.42 root left outer join, inner:HashAgg_88, equal:[eq(tpch.part.p_partkey, tpch.partsupp.ps_partkey)]
├─HashLeftJoin_44 125109.42 root inner join, inner:TableReader_85, equal:[eq(tpch.nation.n_regionkey, tpch.region.r_regionkey)]
│ ├─HashLeftJoin_49 625547.12 root inner join, inner:TableReader_82, equal:[eq(tpch.supplier.s_nationkey, tpch.nation.n_nationkey)]
│ │ ├─IndexJoin_53 625547.12 root inner join, inner:TableReader_52, outer key:tpch.partsupp.ps_suppkey, inner key:tpch.supplier.s_suppkey
│ │ │ ├─IndexJoin_60 625547.12 root inner join, inner:IndexLookUp_59, outer key:tpch.part.p_partkey, inner key:tpch.partsupp.ps_partkey
│ │ │ │ ├─TableReader_76 155496.00 root data:Selection_75
│ │ │ │ │ └─Selection_75 155496.00 cop eq(tpch.part.p_size, 30), like(tpch.part.p_type, "%STEEL", 92)
│ │ │ │ │ └─TableScan_74 10000000.00 cop table:part, range:[-inf,+inf], keep order:false
│ │ │ │ └─IndexLookUp_59 1.00 root
│ │ │ │ ├─IndexScan_57 1.00 cop table:partsupp, index:PS_PARTKEY, PS_SUPPKEY, range: decided by [tpch.part.p_partkey], keep order:false
│ │ │ │ └─TableScan_58 1.00 cop table:partsupp, keep order:false
│ │ │ └─TableReader_52 1.00 root data:TableScan_51
│ │ │ └─TableScan_51 1.00 cop table:supplier, range: decided by [tpch.partsupp.ps_suppkey], keep order:false
│ │ └─TableReader_82 25.00 root data:TableScan_81
│ │ └─TableScan_81 25.00 cop table:nation, range:[-inf,+inf], keep order:false
│ └─TableReader_85 1.00 root data:Selection_84
│ └─Selection_84 1.00 cop eq(tpch.region.r_name, "ASIA")
│ └─TableScan_83 5.00 cop table:region, range:[-inf,+inf], keep order:false
└─HashAgg_88 8155010.44 root group by:tpch.partsupp.ps_partkey, funcs:min(tpch.partsupp.ps_supplycost), firstrow(tpch.partsupp.ps_partkey)
└─HashRightJoin_92 8155010.44 root inner join, inner:HashRightJoin_94, equal:[eq(tpch.supplier.s_suppkey, tpch.partsupp.ps_suppkey)]
├─HashRightJoin_94 100000.00 root inner join, inner:HashRightJoin_100, equal:[eq(tpch.nation.n_nationkey, tpch.supplier.s_nationkey)]
│ ├─HashRightJoin_100 5.00 root inner join, inner:TableReader_105, equal:[eq(tpch.region.r_regionkey, tpch.nation.n_regionkey)]
│ │ ├─TableReader_105 1.00 root data:Selection_104
│ │ │ └─Selection_104 1.00 cop eq(tpch.region.r_name, "ASIA")
│ │ │ └─TableScan_103 5.00 cop table:region, range:[-inf,+inf], keep order:false
│ │ └─TableReader_102 25.00 root data:TableScan_101
│ │ └─TableScan_101 25.00 cop table:nation, range:[-inf,+inf], keep order:false
│ └─TableReader_107 500000.00 root data:TableScan_106
│ └─TableScan_106 500000.00 cop table:supplier, range:[-inf,+inf], keep order:false
└─TableReader_109 40000000.00 root data:TableScan_108
└─TableScan_108 40000000.00 cop table:partsupp, range:[-inf,+inf], keep order:false
└─HashRightJoin_39 125109.42 root inner join, inner:HashLeftJoin_44, equal:[eq(tpch.part.p_partkey, tpch.partsupp.ps_partkey) eq(tpch.partsupp.ps_supplycost, min(ps_supplycost))]
├─HashLeftJoin_44 125109.42 root inner join, inner:TableReader_85, equal:[eq(tpch.nation.n_regionkey, tpch.region.r_regionkey)]
│ ├─HashLeftJoin_49 625547.12 root inner join, inner:TableReader_82, equal:[eq(tpch.supplier.s_nationkey, tpch.nation.n_nationkey)]
│ │ ├─IndexJoin_53 625547.12 root inner join, inner:TableReader_52, outer key:tpch.partsupp.ps_suppkey, inner key:tpch.supplier.s_suppkey
│ │ │ ├─IndexJoin_60 625547.12 root inner join, inner:IndexLookUp_59, outer key:tpch.part.p_partkey, inner key:tpch.partsupp.ps_partkey
│ │ │ │ ├─TableReader_76 155496.00 root data:Selection_75
│ │ │ │ │ └─Selection_75 155496.00 cop eq(tpch.part.p_size, 30), like(tpch.part.p_type, "%STEEL", 92)
│ │ │ │ │ └─TableScan_74 10000000.00 cop table:part, range:[-inf,+inf], keep order:false
│ │ │ │ └─IndexLookUp_59 1.00 root
│ │ │ │ ├─IndexScan_57 1.00 cop table:partsupp, index:PS_PARTKEY, PS_SUPPKEY, range: decided by [tpch.part.p_partkey], keep order:false
│ │ │ │ └─TableScan_58 1.00 cop table:partsupp, keep order:false
│ │ │ └─TableReader_52 1.00 root data:TableScan_51
│ │ │ └─TableScan_51 1.00 cop table:supplier, range: decided by [tpch.partsupp.ps_suppkey], keep order:false
│ │ └─TableReader_82 25.00 root data:TableScan_81
│ │ └─TableScan_81 25.00 cop table:nation, range:[-inf,+inf], keep order:false
│ └─TableReader_85 1.00 root data:Selection_84
│ └─Selection_84 1.00 cop eq(tpch.region.r_name, "ASIA")
│ └─TableScan_83 5.00 cop table:region, range:[-inf,+inf], keep order:false
└─HashAgg_88 8155010.44 root group by:tpch.partsupp.ps_partkey, funcs:min(tpch.partsupp.ps_supplycost), firstrow(tpch.partsupp.ps_partkey)
└─HashRightJoin_92 8155010.44 root inner join, inner:HashRightJoin_94, equal:[eq(tpch.supplier.s_suppkey, tpch.partsupp.ps_suppkey)]
├─HashRightJoin_94 100000.00 root inner join, inner:HashRightJoin_100, equal:[eq(tpch.nation.n_nationkey, tpch.supplier.s_nationkey)]
│ ├─HashRightJoin_100 5.00 root inner join, inner:TableReader_105, equal:[eq(tpch.region.r_regionkey, tpch.nation.n_regionkey)]
│ │ ├─TableReader_105 1.00 root data:Selection_104
│ │ │ └─Selection_104 1.00 cop eq(tpch.region.r_name, "ASIA")
│ │ │ └─TableScan_103 5.00 cop table:region, range:[-inf,+inf], keep order:false
│ │ └─TableReader_102 25.00 root data:TableScan_101
│ │ └─TableScan_101 25.00 cop table:nation, range:[-inf,+inf], keep order:false
│ └─TableReader_107 500000.00 root data:TableScan_106
│ └─TableScan_106 500000.00 cop table:supplier, range:[-inf,+inf], keep order:false
└─TableReader_109 40000000.00 root data:TableScan_108
└─TableScan_108 40000000.00 cop table:partsupp, range:[-inf,+inf], keep order:false
/*
Q3 Shipping Priority Query
This query retrieves the 10 unshipped orders with the highest value.
Expand Down Expand Up @@ -965,21 +964,20 @@ where
l_partkey = p_partkey
);
id count task operator info
Projection_15 1.00 root div(11_col_0, 7.0)
└─StreamAgg_20 1.00 root funcs:sum(tpch.lineitem.l_extendedprice)
└─Projection_43 235019.06 root tpch.lineitem.l_partkey, tpch.lineitem.l_quantity, tpch.lineitem.l_extendedprice, tpch.part.p_partkey, tpch.part.p_brand, tpch.part.p_container, mul(0.2, 7_col_0)
└─Selection_44 235019.06 root lt(tpch.lineitem.l_quantity, mul(0.2, 7_col_0))
└─HashLeftJoin_45 293773.83 root left outer join, inner:HashAgg_39, equal:[eq(tpch.part.p_partkey, tpch.lineitem.l_partkey)]
├─HashRightJoin_51 293773.83 root inner join, inner:TableReader_34, equal:[eq(tpch.part.p_partkey, tpch.lineitem.l_partkey)]
│ ├─TableReader_34 9736.49 root data:Selection_33
│ │ └─Selection_33 9736.49 cop eq(tpch.part.p_brand, "Brand#44"), eq(tpch.part.p_container, "WRAP PKG")
│ │ └─TableScan_32 10000000.00 cop table:part, range:[-inf,+inf], keep order:false
│ └─TableReader_53 300005811.00 root data:TableScan_52
│ └─TableScan_52 300005811.00 cop table:lineitem, range:[-inf,+inf], keep order:false
└─HashAgg_39 9943040.00 root group by:col_3, funcs:avg(col_0, col_1), firstrow(col_2)
└─TableReader_40 9943040.00 root data:HashAgg_35
└─HashAgg_35 9943040.00 cop group by:tpch.lineitem.l_partkey, funcs:avg(tpch.lineitem.l_quantity), firstrow(tpch.lineitem.l_partkey)
└─TableScan_38 300005811.00 cop table:lineitem, range:[-inf,+inf], keep order:false
Projection_14 1.00 root div(11_col_0, 7.0)
└─StreamAgg_19 1.00 root funcs:sum(tpch.lineitem.l_extendedprice)
└─Projection_42 293773.83 root tpch.lineitem.l_partkey, tpch.lineitem.l_quantity, tpch.lineitem.l_extendedprice, tpch.part.p_partkey, tpch.part.p_brand, tpch.part.p_container, mul(0.2, 7_col_0)
└─HashRightJoin_44 293773.83 root inner join, inner:HashRightJoin_28, equal:[eq(tpch.part.p_partkey, tpch.lineitem.l_partkey)], other cond:lt(tpch.lineitem.l_quantity, mul(0.2, 7_col_0))
├─HashRightJoin_28 293773.83 root inner join, inner:TableReader_33, equal:[eq(tpch.part.p_partkey, tpch.lineitem.l_partkey)]
│ ├─TableReader_33 9736.49 root data:Selection_32
│ │ └─Selection_32 9736.49 cop eq(tpch.part.p_brand, "Brand#44"), eq(tpch.part.p_container, "WRAP PKG")
│ │ └─TableScan_31 10000000.00 cop table:part, range:[-inf,+inf], keep order:false
│ └─TableReader_30 300005811.00 root data:TableScan_29
│ └─TableScan_29 300005811.00 cop table:lineitem, range:[-inf,+inf], keep order:false
└─HashAgg_59 9943040.00 root group by:col_3, funcs:avg(col_0, col_1), firstrow(col_2)
└─TableReader_60 9943040.00 root data:HashAgg_56
└─HashAgg_56 9943040.00 cop group by:tpch.lineitem.l_partkey, funcs:avg(tpch.lineitem.l_quantity), firstrow(tpch.lineitem.l_partkey)
└─TableScan_37 300005811.00 cop table:lineitem, range:[-inf,+inf], keep order:false
/*
Q18 Large Volume Customer Query
The Large Volume Customer Query ranks customers based on their having placed a large quantity order. Large
Expand Down
1 change: 1 addition & 0 deletions cmd/explaintest/t/explain_easy.test
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Expand Up @@ -70,6 +70,7 @@ explain select * from t where b = 1 and b = 2;
drop table if exists t;
create table t(a bigint primary key);
explain select * from t where a = 1 and a = 2;
explain select null or a > 1 from t;

drop table if exists ta, tb;
create table ta (a varchar(20));
Expand Down
37 changes: 31 additions & 6 deletions expression/constant_fold.go
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Expand Up @@ -86,18 +86,43 @@ func foldConstant(expr Expression) (Expression, bool) {
}

args := x.GetArgs()
canFold := true
sc := x.GetCtx().GetSessionVars().StmtCtx
argIsConst := make([]bool, len(args))
hasNullArg := false
allConstArg := true
isDeferredConst := false
for i := 0; i < len(args); i++ {
foldedArg, isDeferred := foldConstant(args[i])
x.GetArgs()[i] = foldedArg
_, conOK := foldedArg.(*Constant)
if !conOK {
canFold = false
}
con, conOK := foldedArg.(*Constant)
argIsConst[i] = conOK
allConstArg = allConstArg && conOK
hasNullArg = hasNullArg || (conOK && con.Value.IsNull())
isDeferredConst = isDeferredConst || isDeferred
}
if !canFold {
if !allConstArg {
if !hasNullArg || !sc.InNullRejectCheck || x.FuncName.L == ast.NullEQ {
return expr, isDeferredConst
}
constArgs := make([]Expression, len(args))
for i, arg := range args {
if argIsConst[i] {
constArgs[i] = arg
} else {
constArgs[i] = One
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Would it be incorrect if the ScalarFunction is NullEQ?

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is null and is not null should have only one parameter, so they would not fall into code path of this patch IMHO.

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What I mentioned here is the operator <=>.

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Oh you are right, will fix this, thanks.

}
}
dummyScalarFunc := NewFunctionInternal(x.GetCtx(), x.FuncName.L, x.GetType(), constArgs...)
value, err := dummyScalarFunc.Eval(chunk.Row{})
if err != nil {
return expr, isDeferredConst
}
if value.IsNull() {
return &Constant{Value: value, RetType: x.RetType}, false
}
if isTrue, err := value.ToBool(sc); err == nil && isTrue == 0 {
return &Constant{Value: value, RetType: x.RetType}, false
}
return expr, isDeferredConst
}
value, err := x.Eval(chunk.Row{})
Expand Down
70 changes: 63 additions & 7 deletions plan/logical_plan_test.go
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Expand Up @@ -286,9 +286,8 @@ func mockContext() sessionctx.Context {
func (s *testPlanSuite) TestPredicatePushDown(c *C) {
defer testleak.AfterTest(c)()
tests := []struct {
sql string
first string
best string
sql string
best string
}{
{
sql: "select count(*) from t a, t b where a.a = b.a",
Expand Down Expand Up @@ -548,8 +547,8 @@ func (s *testPlanSuite) TestOuterWherePredicatePushDown(c *C) {
}{
// issue #7628, left join with where condition
{
sql: "select * from t as t1 left join t as t2 on t1.b = t2.b where (t1.a=1 and t2.a=1) or (t1.a=2 and t2.a=2)",
sel: "[or(and(eq(t1.a, 1), eq(t2.a, 1)), and(eq(t1.a, 2), eq(t2.a, 2)))]",
sql: "select * from t as t1 left join t as t2 on t1.b = t2.b where (t1.a=1 and t2.a is null) or (t1.a=2 and t2.a=2)",
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Why change this?

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The purpose of this test case is to verify predicate pushdown over outer join, after applying this PR, the outer join would be converted to inner join now, so I changed the where condition to keep the outer join.

sel: "[or(and(eq(t1.a, 1), isnull(t2.a)), and(eq(t1.a, 2), eq(t2.a, 2)))]",
left: "[or(eq(t1.a, 1), eq(t1.a, 2))]",
right: "[]",
},
Expand All @@ -560,8 +559,8 @@ func (s *testPlanSuite) TestOuterWherePredicatePushDown(c *C) {
right: "[]",
},
{
sql: "select * from t as t1 left join t as t2 on t1.b = t2.b where (t1.c=1 and ((t1.a=3 and t2.a=3) or (t1.a=4 and t2.a=4))) or (t1.a=2 and t2.a=2)",
sel: "[or(and(eq(t1.c, 1), or(and(eq(t1.a, 3), eq(t2.a, 3)), and(eq(t1.a, 4), eq(t2.a, 4)))), and(eq(t1.a, 2), eq(t2.a, 2)))]",
sql: "select * from t as t1 left join t as t2 on t1.b = t2.b where (t1.c=1 and ((t1.a=3 and t2.a=3) or (t1.a=4 and t2.a=4))) or (t1.a=2 and t2.a is null)",
sel: "[or(and(eq(t1.c, 1), or(and(eq(t1.a, 3), eq(t2.a, 3)), and(eq(t1.a, 4), eq(t2.a, 4)))), and(eq(t1.a, 2), isnull(t2.a)))]",
left: "[or(and(eq(t1.c, 1), or(eq(t1.a, 3), eq(t1.a, 4))), eq(t1.a, 2))]",
right: "[]",
},
Expand Down Expand Up @@ -593,6 +592,63 @@ func (s *testPlanSuite) TestOuterWherePredicatePushDown(c *C) {
}
}

func (s *testPlanSuite) TestSimplifyOuterJoin(c *C) {
defer testleak.AfterTest(c)()
tests := []struct {
sql string
best string
joinType string
}{
{
sql: "select * from t t1 left join t t2 on t1.b = t2.b where t1.c > 1 or t2.c > 1;",
best: "Join{DataScan(t1)->DataScan(t2)}(t1.b,t2.b)->Sel([or(gt(t1.c, 1), gt(t2.c, 1))])->Projection",
joinType: "left outer join",
},
{
sql: "select * from t t1 left join t t2 on t1.b = t2.b where t1.c > 1 and t2.c > 1;",
best: "Join{DataScan(t1)->DataScan(t2)}(t1.b,t2.b)->Projection",
joinType: "inner join",
},
{
sql: "select * from t t1 left join t t2 on t1.b = t2.b where not (t1.c > 1 or t2.c > 1);",
best: "Join{DataScan(t1)->DataScan(t2)}(t1.b,t2.b)->Projection",
joinType: "inner join",
},
{
sql: "select * from t t1 left join t t2 on t1.b = t2.b where not (t1.c > 1 and t2.c > 1);",
best: "Join{DataScan(t1)->DataScan(t2)}(t1.b,t2.b)->Sel([not(and(le(t1.c, 1), le(t2.c, 1)))])->Projection",
joinType: "left outer join",
},
{
sql: "select * from t t1 left join t t2 on t1.b > 1 where t1.c = t2.c;",
best: "Join{DataScan(t1)->DataScan(t2)}(t1.c,t2.c)->Projection",
joinType: "inner join",
},
{
sql: "select * from t t1 left join t t2 on true where t1.b <=> t2.b;",
best: "Join{DataScan(t1)->DataScan(t2)}->Sel([nulleq(t1.b, t2.b)])->Projection",
joinType: "left outer join",
},
}
for _, ca := range tests {
comment := Commentf("for %s", ca.sql)
stmt, err := s.ParseOneStmt(ca.sql, "", "")
c.Assert(err, IsNil, comment)
p, err := BuildLogicalPlan(s.ctx, stmt, s.is)
c.Assert(err, IsNil, comment)
p, err = logicalOptimize(flagPredicatePushDown|flagPrunColumns, p.(LogicalPlan))
c.Assert(err, IsNil, comment)
c.Assert(ToString(p), Equals, ca.best, comment)
join, ok := p.(LogicalPlan).Children()[0].(*LogicalJoin)
if !ok {
join, ok = p.(LogicalPlan).Children()[0].Children()[0].(*LogicalJoin)
c.Assert(ok, IsTrue, comment)
}
joinType := fmt.Sprintf("%s", join.JoinType.String())
c.Assert(joinType, Equals, ca.joinType, comment)
}
}

func newPartitionInfoSchema(definitions []model.PartitionDefinition) infoschema.InfoSchema {
tableInfo := *MockTable()
cols := make([]*model.ColumnInfo, 0, len(tableInfo.Columns))
Expand Down
7 changes: 5 additions & 2 deletions plan/rule_predicate_push_down.go
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Expand Up @@ -260,15 +260,18 @@ func simplifyOuterJoin(p *LogicalJoin, predicates []expression.Expression) {
// If it is a conjunction containing a null-rejected condition as a conjunct.
// If it is a disjunction of null-rejected conditions.
func isNullRejected(ctx sessionctx.Context, schema *expression.Schema, expr expression.Expression) bool {
expr = expression.PushDownNot(nil, expr, false)
sc := ctx.GetSessionVars().StmtCtx
sc.InNullRejectCheck = true
result := expression.EvaluateExprWithNull(ctx, schema, expr)
sc.InNullRejectCheck = false
x, ok := result.(*expression.Constant)
if !ok {
return false
}
sc := ctx.GetSessionVars().StmtCtx
if x.Value.IsNull() {
return true
} else if isTrue, err := x.Value.ToBool(sc); err != nil || isTrue == 0 {
} else if isTrue, err := x.Value.ToBool(sc); err == nil && isTrue == 0 {
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should it be err == nil && isTrue != 0?

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isTrue != 0 means the where condition is true if the inner table columns are null, so it cannot be rejected?

return true
}
return false
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1 change: 1 addition & 0 deletions sessionctx/stmtctx/stmtctx.go
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Expand Up @@ -60,6 +60,7 @@ type StatementContext struct {
UseCache bool
PadCharToFullLength bool
BatchCheck bool
InNullRejectCheck bool
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Can we make this an input parameter for foldConstant?

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If we make it a parameter of foldConstant, we have to modify signature of FoldConstant, NewFunction, NewFunctionInternal, EvaluateExprWithNull, this would lead to a lot of unnecessary code changes


// mu struct holds variables that change during execution.
mu struct {
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